'Sensei' is appropriate for all instructors. A master may be referred to as Hanshi, but we only use the title when talking with others, not as a form of address when talking with him.
depends on what usage master as in instructor sensei
It is Japanese and means 'master instructor' usually used in the martial arts for a mid-grade instructor.
A karate instructor is not required to have any academic qualifications.
A sensei.
Step 1: Join a club Step 2: Do whatever the Instructor tells you
He delivered more kicks in one night than the karate instructor did in all his years of teaching!
dre's instructor is g.Han
Sensei is the Japanese word for teacher. Many styles of Karate will refer to their instructors as sensei. However, lower graded black belts who instruct may be referred to as senpai, meaning senior student, and highly graded or senior black belts will be referred to as Shihan/hanshi meaning master or expert. Some of these senior grades may choose to be referred to as sensei, as a way of being less removed from his/her students
There is no single master.
There was no single master - karate encompasses the product of an enormous number of practitioners.
karate is Japanese
You don't master karate at brown belt. You don't normally ever master karate. The best thing to do is to practice often and hard.